Axial flow compressor or fan and gas turbine engine provided therewith



May? l1, 1965 C. T. HEwsoN v3,182,893

AXIAL FLOW COMPRESSOR OR FAN AND GAS TURBINE ENGINE PROV'IDED THEREWITH Filed May 25, 1965 2 sheets-smet 1 raz;

May 141', 1965 A c. T. HEwsoN 3,182,893 A n AXIAL FLOW COMPRESSORv OR` FAN AND GAS I '.IURBINEl ENGINE PROVIDED THEREWITH 4Filed May 23; 196s 2 Sheets-Sheet 2 United States Patent O 3,182,898 AXIAL FLOW COMPRESSOR R FAN AND GAS TINE ENGNE PROVEDED TlmREWITH Colin Taylor Hewson, Derby, England, assigner to Rolls- Royce Limited, Derby, England, a company of Great Britain Filed May 23, 1963, Ser. No. 282,788

Claims priority, application Great Britain, May 31, 1962,

,106 Claims. (Cl. 23d-116) This invention concerns a gas turbine by-pass engine.

According to the present invention there is provided a gas turbine by-pass engine comprising a rst shaft, a second shaft mounted within said first shaft, a high pressure compressor and a high pressure turbine each having at least one row of rotor blades drivingly engaged with said rst shaft, a low pressure compressor and a low pressure turbine each having at least one row of rotor blades engaged with said second shaft, a by-pass duct which communicates with the downstream end of the low pressure compressor so as to receive part of the air compressed thereby, a rotatable casing forming part of the low pressure compressor, at least one row of rotatable guide blades which are carried by the rotatable casing and which are driven by air passing through the low pressure compressor, and a driven part which requires substantial torque to drive it and which is -drivingly connected to the rotatable casing.

It will be appreciated that, even if the rotor blades of the low pressure compressor are driven at a very high speed, the relative tip speed of each row of rotor blades with respect to the tip `speed of the row of rotatable guide blades immediately upstream of it may readily be arranged so that the relative air velocity is subsonic. Thus the difficulties which arise when the compressor rotor blades are rotatated at very high tip speeds approaching sonic speed may be avoided.

The amount of work transmitted to the rotatable guide blades may be arranged to be up to 60% or more of the amount of work transmitted to the rotor blades, while the speed of the rotatable guide blades may, for example, be arranged to be 30-40% of the speed of the rotor blades.

If the row or rows of rotatable guide blades are arranged to drive a propeller or tan, the relative rotational speed of the rotatable guide blades and of the rotor blades may readily be arranged to be such that the rotatable guide blades rotate at the correct speed for the propeller or fan, whereby the use of intermediate gearing may be avoided.

The ability to dispense with such gearing not only in itself represents a saving in weight and complexity but also enables a front fan to `be driven from the front end of the compressor without any mechanical connection to a shaft on which the rotor blades are mounted.

The invention is thus applicable to ducted fan by-pass engines.

A brake may be provided which, when engaged prevents rotation of the row or rows of rotatable guide blades.

The fan driven by the rotatable guide blades may be arranged in an annular fan duct, the said duct surrounding a casing within which the rotor and stator blades are mounted.

The invention is illustrated, merely by way of example in the accompanying drawings, in which:

FIGURES 1-5 are broken away sections of a number of different gas turbine engines provided with compressors according to the present invention.

In FIGURE 1 is shown a two-shaft by-pass gas turbine engine which has a low pressure compressor 170 having four rows 170a of rotor Iblades driven through ice a shaft 168 by a single row 171a of rotor blades of a low pressure turbine 171. The said engine also has a high pressure compressor 172 having eight rows 172e of rotor blades driven through a shaft 169 by a single row 173g of rotor blades of a high pressure turbine 173, the shaft 168 being arranged concentrically within the shaft 169.

A by-pass duct 165 communicates with the downstream. end of the low pressure compressor 170 so as to receive part of the air compressed thereby, the by-pass duct 165 by-passing the high pressure compressor 172, combustion equipment 166, and the turbines 173, 171. The low pressure compressor 170 has a row 167 of rotatable inlet guide vanes and three rows 174 of rotatable guide blades carried by a casing 175 which is rotatably mounted by means of bearings 176 and 177. The rows 174 of rotatable guide blades are driven by air passing through the low pressure compressor 170.

The tip speed of the rotatable guide blades may therefore be arranged to be substantially less than, although related to, that of the rotor blades. Even, therefore, if the rows 170a of rotor blades are driven at a very high speed, the relative tip speed of each of the rows 179er of rotor blades with respect to that of the rows 174 of rotatable guide blades may readily be arranged so that the relative air velocity is subsonic.

The casing 175 carries two rows 144er of fan rotor blades which are disposed within an annular duct 145:1 which `surrounds the casing 175. The rows 1Mo form part of a front fan, the latter having an annular outer casing 147:1 which supports two rows 146o of fixed vanes.

The low pressure compressor 170 may also, if desired, be provided with a row (not shown) of rotatable outlet guide vanes.

The pressure of the air stream produced by a fan as shown in FIGURE 1 may be arranged, if desired, to be widely different from that produced by the compressors of the engine. The fan air stream may be kept wholly separate from the compressor air stream and the fan may be used as a pump e.g. for boundary layer suction, for supplying air to vertical lift fans, or to provide control air for effecting attitude control during vertical take 01T and landing.

The use of rotatable guide blades (as opposed to the conventionals stator blades) on a by-pass gas turbine engine has particular value because, for a given by-pass ratio, the use of rotatable guide blades on the low pressure compressor results in a smaller frontal area. This arises because the relative velocity of the rotor blades with respect to the guide blades on the low pressure compressor is reduced. This enables a higher axial Velocity to be employed for the travel of air through the low pressure compressor and in turn enables a smaller frontal area to be used, with consequent lightening of the compressor. Although the use of rotatable guide blades will give this advantage on all gas turbine engines to some extent, their use has the greatest value on by-pass engines having a high by-pass ratio.

In FIGURE 2 there is shown a by-pass gas turbine engine 10k which has a single stage high pressure turbine k and a single stage low pressure turbine 131k. The rotor blades of the high pressure turbine 130k, via a shaft 132k, drives rows 133k of rotor blades of a high pressure compressor 134k, the high pressure compressor 134k having fixed stator blades 135k which are carried by the engine casing 136k.

The rotor blades of the low pressure turbine 131k, Via a shaft 137k which is mounted concentrically within the shaft 132k, drives four rows 140k Iof rotor blades of a low pressure compressor 141k. Between each adjacent pair of rows 140k there is a row 142k of rotatable guide blades,

areaaes the low pressure compressor 141k also being provided with a row 167k of rotatable inlet guide vanes. The rows 142k, 167k are mounted in a rotatable annular casing 143k which carries three rows 144k of fan rotor blades which are disposed within an annular fan duct 145k which surrounds the casing 143k. The rows 144k, which form part of a front fan, are respectively disposed between rows 146k of fixed vanes which support an annular outer casing 147k.

The engine k, in addition to being a ducted yfan engine is a by-pass engine having a by-pass passage 165k. The latter, which receives part of the air compressed in the low pressure compressor 141k and which also receives the air which has passed through the fan duct 145k, annularly surrounds the engine casing 136k. It is of course necessary to arrange that the fan pressure ratio is made approximately the same as the pressure ratio of the low pressure compressor.

Use of the rotatable guide blades to drive a ducted fan as shown in FIGURE 2, in a by-pass engine, has the advantage that it enables a very high by-pass ratio to be achieved. Thus a by-pass engine of the kind employing a high pressure ratio and high temperatures can be made to produce a higher by-pass ratio by using this invention. All that is necessary is to replace the low pressure compressor stator blades by rotatable guide blades and use the rotatable guide blades to drive a fan. If, moreover, this is done, fewer low pressure turbine stages need be used, because the low pressure shaft can rotate faster than normal because the tip speeds of the blades may readily be arranged to be subsonic.

The stream of air which has passed through the fan duct 145k could be arranged to join the by-pass stream and the jet efiiux in a common plane or the two said streams could be mixed through by-pass mixers (not shown) which might consist of short stub pipes extending from the fan duct to the by-pass passage. Alternatively, the short stub pipes could extend through to the jet passage so as to mix one or both lof the said streams with the jet gases before they pass through the final nozzle.

FIGURE 3 shows a by-pass gas turbine engine of the type which employs an intermediate compressor. The engine comprises a low pressure compressor 178 having rows 178a of rotor blades driven through a shaft 178b by the rotor blades of a two stage low pressure turbine 179. An intermediate compressor 180 has rows 180a of rotor blades driven through the shaft 178b by the same turbine 179. A high pressure compressor 181 has rows 181a of rotor blades which are driven through a shaft 181b by the rotor blades of a high pressure turbine 182. The shaft 178b is mounted concentrically within the shaft 181b.

The low pressure compressor 178 has three stages 183 of rotatable guide blades and a row 188 of rotatable inlet guide vanes which are carried by a casing 184 which is rotatably mounted by means of bearings 185 and 186.

The casing 184 carries two rows 144b of fan rotor blades which are disposed within an annular duct 145b which surrounds the casing 184. The rows 14411 form part of a front fan, the latter having an annular outer casing 147b which supports two rows 146b of fixed vanes.

A by-pass duct 16517 communicates with the downstream end of the low pressure compressor 178 so as to receive part of the air compressed thereby, the by-pass duct 165b by-passing the compressors 180, 181 and the turbines 182, 179.

In by-pass gas turbine engines employing an intermediate compressor, one of the difficulties is that the speed of the intermediate compressor is limited in practice by the speed of the low pressure compressor and so it is not possible to run the intermediate compressor at the maximum efficiency. By using rotatable guide blades it becomes possible to speed up the low pressure compressor without getting into diiculties because of the approach to sonic tip speeds and this in turn enables the intermediate compressor to be speeded up. This enables the intermediate compressor to be designed so that it is physically smaller but runs faster and passes the same mass ow. The whole problem of matching the low pressure and intermediate compressors is eased and a higher by-pass ratio can be achieved with a smaller frontal area.

FIGURE 4 shows a by-pass gas turbine engine of the same type as is shown in FIGURE 3, the difference being that rotatable guide blades 183g are used to drive three rows 187 of fan rotor blades of a ducted fan. The stream of air produced by the said ducted fan is introduced into by-pass passage 165C by way of short stub pipes 189.

The stator blades of the intermediate compressors shown in FIGURES 3 and 4 may instead, be arranged to be rotatable and may be coupled to the rotatable guide blades of the low pressure compressor, whereby the torque from the rotatable stator blades of the intermediate compressor may form part of the torque used in driving the fan rotor blades. If this is done, a substantially higher by-pass ratio may be achieved.

In FIGURE 5 there is shown a by-pass gas turbine engine 10m which is generally similar to that of FIG. 2 and which will not therefore be described in detail. In the gas turbine engine 10m, however, the downstream end of t le by-pass passage 165m communicates with the engine jet pipe 207 by way of short mixer chutes 208, while the fan duct 145m, which in effect forms a second by-pass passage, does not communicate with the by-pass passage 165m but communicates with the jet pipe 207 by way of short mixer chutes 209 which are arranged downstream of the mixer chutes 208.

The arrangement shown in FIG. 5 permits a conventional thrust reveresr or deilector (not shown) to be arranged at the downstream end of the jet pipe 207. It also has the advantage of providing a greater thrust and a higher by-pass ratio than that obtainble from the engine of FIG. 2. This greater thrust is obtainable because the pressure in the jet pipe 207 is lower than the pressure at the downstream end of the low pressure compressor 141m so that a lower fan delivery pressure is required to obtain satisfactory mixing at the chutes 209.

As will be appreciated from the above description, the invention permits part of the torque produced by a gas turbine engine to be employed, via the rotatable guide blades, in the driving of a driven part (such as a propel- 1er, not shown, fan rotor blades 144m, a rudder, not shown, a helicopter rotor, not shown, or electricity generating plant, not shown), which requires substantial torque to drive it.

In FIGURE 6 there is shown a gas turbine engine 10d having a one-stage turbine 14d which drives a shaft 16d. The shaft 16d drives rows 71, 72, 73 of rotor blades of a high pressure compressor 74, the latter also being provided with rows 75, 76, 77 of rotatable guide blades.

The rows 75, 76, 77 of rotatable guide blades are mounted in an annular casing which is rotatably mounted within an annular casing 81. The casing 81 carries ixed outlet guide vanes 82 of the high pressure compressor 74.

The engine 10d, also has a low pressure compressor 83 which has rows 84, 85 of fixed stator blades, the row being carried by the casing 81.

The low pressure compressor 83 has a rotor 86 which carries rows 87, 88 of rotor blades. The rotor 86 is drivingly connected by a radially extending annular member 9 to the casing 80 and so to the rows 7S, 76, 77 of rotatable guide blades.

Thus the rotatable guide blades of the high pressure compressor 74 are used to drive the rotor blades of the low pressure compressor 83, whereby only a single turbine 14d has to be employed.

I claim:

l. A gas turbine by-pass engine comprising a first shaft, a second shaft mounted within said first shaft, a high pressure compressor and a high pressure turbine each having at least one row of rotor blades drivingly engaged with said first shaft, a low pressure compressor and a low pressure turbine each having at least one row of rotor blades engaged with said second shaft, a by-pass duct which communicates with the downstream end of the low pressure compressor so as to receive part of the air compressed thereby, a rotatable casing forming part of the low pressure compressor, at least one row of rotatable guide blades which are carried by the rotatable casing and which are driven by air passing through the low pressure compressor, and a driven part which requires substantial toque to dive it and which is drivingly connected to the rotatable casing.

2. A gas turbine by-pass engine comprising a rst shaft, a second shaft mounted within said first shaft, a high pressure compressor and a high pressure turbine each having at least one row of rotor blades drivingly engaged with said first shaft, a low pressure compressor and a low pressure turbine each having at least one `row of rotor blades engaged with said second shaft, a by-pass duct which communicates with the downstream end of the low pressure compressor so as to receive part of the air compressed thereby, a rotatable casing forming part of the low pressure compressor, at least one row of rotatable guide blades which are carried by the rotatable casing and which are driven by air passing through the low pressure compressor, an annular fan duct which concentrically surrounds the low pressure compressor, and a fan having at least one row of fan rotor blades which are arranged in the fan duct and which are driven by the rotatable guide blades.

V3. A gas turbine by-pass engine comprising a first shaft, a second shaft mounted within said first shaft, a high pressure compressor and a high pressure turbine each having at least one row of rotor blades drivingly engaged with said rst shaft, a low pressure compressor and a low pressure turbine each having at least one row of rotor blades engaged with said second shaft, a by-pass duct which communicates with the downstream end of the low pressure compressor so as to receive part of the air compressed thereby, a rotatable casing forming part of the low pressure compressor, at least one row of rotatable guide blades which are carried by the rotatable casing and which are driven by air passing through the loW pressure compressor, an annular fan duct which concentrically surrounds the low pressure compressor, and a fan having at least one row of fan rotor blades which are arranged in the fan duct and which are driven by therotatable guide blades, the downstream end of the fan duct cornmunicating with the by-pass duct.

4. A gas turbine by-pass engine comprising a lirst shaft, a second shaft mounted within said first shaft, a high pressure compressor and a high pressure turbine, each having at least one row of rotor blades drivingly engaged with said rst shaft, a low pressure compressor, an intermediate pressure compressor and a W pressure turbine, each having at least one row of rotor blades engaged with said second shaft, :a by-pass duct which communicates with the downstream end of the low pressure compressor so as to receive part of the air compressed thereby, a rotatable casing forming part of the low pressure compressor, at least one row of rotatable guide blades which are carried by the rotatable casing and'which are driven by air passing through the 10W pressure compressor, and a driven part which requires substantial torque to drive it and which is drivingly connected to the rotatable casing.

5. A gas turbine by-pass engine comprising a first shaft, a second shaft mounted within said first shaft, a high pressure compressor [and a high pressure turbine, each having at least one row of rotor blades drivingly engaged with said rst shaft, a low pressure compressor, an intermediate pressure compressor and a low pressure turbine, each having at least one row of rotor blades engaged with said second shaft, -a -by-pass duct which communicates with the downstream end of the low pressure compressor so as to receive part of the air compressed thereby, a rotatable casing forming part of the low pressure compressor, at least one row of rotatable guide blades whichare carried by the rotatable casing and which are driven by air passing through the low pressure compressor, an annular fan duct which concentrically surroundsthe low pressure compressor, and a fan having at least one row of fan rotor blades which are arranged in the fan duct and which are driven by the rotatable guide blades.

`6. A gas turbine by-pasa engine comprising a irst shaft, a second shaft mounted within said firstrshaft, a high pre"- sure compressor and a high pressure turbine, each having at least one row of rotor blades drivingly engaged with said first shaft, a low pressure compressor, an intermediate pressure compressor and a low pressure turbine, each having at least one row of rotor blades engaged with said second shaft, a by-pass duct which communicates with the downstream end of the low pressure compressor so as to receive part of the air compressed thereby, a rotatable casing forming part of the low pressure compressor, at least one row of rotatable guide blades which are carried by the rotatable casing and which are driven by air passing through the low pressure compressor, an annular fan duct which concentrically surrounds the low pressure compressor and a fan having at least one row of fan rotor blades which are arranged in the fan duct and which are driven by the rotatable guide blades, and stub pipes through which the downstream end of the fan duct communicates with the by-pass duct.

7. A gas turbine by-pass engine comprising an axial tlow compressor having at least one row of rotatable guide blades and a row of rotor blades mounted immediately adjacent to the row of rotatable guide blades, a bypass passage receiving some of the air compressed in the compressor, an annular fan duct arranged outwardly of and concentric with the by-pass passage, and a fan arranged in the fan duct yand driven by the rotatable guide blades.

8. A gas turbine by-pass engine as claimed in claim 7 in which the annular fan duct communicates with the by-pass passage.

9. A gas turbine by-pass engine as claimed in claim 7 in which the by-pass passage communicates with the engine jet pipe, the annular fan duct communicating with the jet pipe in a region downstream of the region in which the by-pass passage communicates with the jet pipe.

l0. A gas turbine engine as claimed in claim 7 in which the engine is provided with a high pressure compressor, a high pressure turbine driving-the high pressure compressor, a low pressure turbine and low and intermediate pressure compressors which are driven by the low pressure turbine.

References Cited by the Examiner UNITED STATES PATENTS 2,450,745 10/ 48 Baumann 230-122 X 2,659,528 1l/53 Price 253-77 2,7 02,985 3/55 Howell 253-77 FOREIGN PATENTS 676,769 8/52 Great Britain.

65,557 4/50 The Netherlands.

' LAURENCE v. EFNER, Primm Examiner.

ROBERT M. WALKER, Examiner. Y 

1. A GAS TURBINE BY-PASS ENGINE COMPRISING A FIRST SHAFT, A SECOND SHAFT MOUNTED WITHIN SAID FIRST SHAFT, A HIGH PRESSURE COMPRESSOR AND A HIGH PRESSURE TURBINE EACH HAVING AT LEAST ONE ROW OF ROTOR BLADES DRIVINGLY ENGAGED WITH SAID FIRST SHAFT, A LOW PRESSURE COMPRESSOR AND A LOW PRESSURE TURBINE EACH HAVING AT LEAST ONE ROW OF ROTOR BLADES ENGAGED WITH SAID SECOND SHAFT, A BY-PASS DUCT WHICH COMMUNICATES WITH THE DOWNSTREAM AND OF THE LOW PRESSURE COMPRESSOR SO AS TO RECEIVE PART OF THE AIR COMPRESSED THEREBY, A ROTATABLE CASING FORMING PART OF THE LOW PRESSURE COMPRESSOR, AT LEAST ONE ROW OF ROTATABLE GUIDE BALDES WHICH ARE CARRIED BY THE ROTATABLE CASING AND WHICH ARE DRIVEN BY AIR PASSING THROUGH THE LOW PRESSURE COMPRESSOR, AND A DRIVEN PART WHICH REQUIRES SUBSTANTIAL TORQUE TO DRIVE IT AND WHICH IS DRIVINGLY CONNECTED TO THE ROTATABLE CASING. 